In general, as a printing device which prints a printing image on a surface of a can barrel of a beverage can, as described in patent literature 1, there has been used, for example, a device which applies printing to a cylindrical can barrel by rotating a resin-made printing plate wound around a peripheral surface of a cylindrical metal-made sleeve body.
A printing plate used in the printing device is used for flexographic printing which is one of letterpress printing methods which use liquid ink (water-based ink or UV ink). Recently, with the progress of laser engraving and printing technology, a printed relief (printing pattern) of high precision can be engraved on the printing plate and hence, a demand for the printing plate has been increasing.
As a raw material for a printing plate which enables direct plate making by laser graving, for example, a nylon-based plate-like photosensitive resin can be named. To use such a photosensitive resin as a raw material for a printing plate, first, it is necessary to cure the photosensitive resin by irradiating an ultraviolet ray to the photosensitive resin to give predetermined strength to the photosensitive resin. Then, the cured photosensitive resin is engraved by a CO2 laser thus forming a printed relief (characters or an image pattern) to be printed on a can barrel.
Two plate-like printing plates having such a configuration are prepared, and these printing plates are wound around a peripheral surface of a cylindrical metal-made sleeve body thus forming a sleeve printing plate. Then, a plurality of sleeve printing plates are mountable on an outer peripheral surface of a cylinder of the printing device for inks of respective colors.
Then, the printing device temporarily transfers ink which follows the printed relief on the printing plate on a blanket formed in a circular cylindrical shape and, thereafter, ink is printed on the can barrel (so-called offset printing).